1. Field of the Invention
This invention relates to a powder-actuated fastener-driving device, and more particularly to a powder-actuated fastener-driving device having sound-absorbing function.
2. Description of the Related Art
Referring to FIG. 1, a conventional powder-actuated fastener-driving device 1 is operable in a single shot mode, and includes a hollow body 11 having a tubular portion 111 at a front end thereof, an inner tube 12 movable forwardly and rearwardly, a cartridge-receiving sleeve 13 connected to the inner tube 12 and having a rear end formed with an accommodating chamber 131 for accommodating a powder cartridge (not shown), a piston 14 movable forwardly and rearwardly and driven by the powder cartridge when the powder cartridge is ignited, and a firing device 15 for igniting the powder cartridge. The inner tube 12 is formed with a slot 121 extending along a front-to-rear direction. The tubular portion 111 is provided with a stop member unit 16 that includes a stop member 161 extending into the slot 121 and biased by a spring to press against the inner tube 12. For safety concern, during use, to change the device 1 into a ready-to-fire state, the device 1 needs to be pressed against a workpiece to move the inner tube 12 rearwardly and compress a firing-device biasing spring, so that the charge cannot be detonated by inadvertent actuation of the trigger device. After a nail shooting operation, to return the piston 14 to its original position in preparation for performing a subsequent nail shooting operation, it is necessary to pull the inner tube 12 forwardly. During forward movement of the inner tube 12, the piston 14 comes into contact with the stop member 161 to thereby move rearwardly in the inner tube 12. Thereafter, the inner tube 12 is pushed rearwardly back to its original position, thereby returning the piston 14 to its original position.
The tubular portion 111 is formed with an aperture 112 in a wall thereof such that, when the inner tube 12 is pulled forwardly to a front limit position, the cartridge-receiving sleeve 13 is exposed within the aperture 112 to allow for replacement of the powder cartridge in the accommodating chamber 131 in the cartridge-receiving sleeve 13.
When the powder cartridge is ignited, combustion gas produced due to explosion of powder in the powder cartridge is sprayed into the atmosphere via the slot 121 in the inner tube 12. Rapid expansion of the gas results in a relatively large amount of noise. Furthermore, flow of the gas through the aperture 112 in the tubular portion 111 also results in generation of noise.
To reduce the noise, many different designs of fastener-driving devices have been proposed. For example, a push rod is provided to push and return the piston 14 to its original position. As such, the slot 121 can be omitted. Use of the push rod, however, affects adversely the operating efficiency of the fastener-driving device. In addition, U.S. Pat. No. 7,575,139 employs nails having a specific structure, thereby increasing the manufacturing costs of the nails. As a result, the fastener-driving devices 2 including the slots 121 and the stop members 161 are still used widely, and it is desirable that the fastener-driving device 2 has a sound-absorbing function.
U.S. Pat. No. 3,743,048 discloses an improved powder-actuated fastener-driving device having a sound-absorbing function and including a sound-absorbing sleeve (i.e., sound muffler) disposed fixedly on a barrel or inner tube. However, the improved powder-actuated fastener-driving device suffers from the following disadvantages:
(1) As long as a force is applied to the sound-absorbing sleeve to move the sound-absorbing sleeve rearwardly relative to a handle of the improved powder-actuated fastener-driving device, the inner tube is moved synchronously with the sound-absorbing sleeve and thereby the device will be changed into a ready-to-fire state without pressing the inner tube against the workpiece. As a consequence, the improved powder-actuated fastener-driving device is dangerous during use.(2) A large amount of powder residue is inevitably built-up within the inner tube, and is deposited on a piston or driving ram and the inner surface of the inner tube, in view of the fact that the gas flows from the inner tube 12 via a front end portion of the inner tube 12, thereby affecting adversely movement of the piston or driving ram within a housing.(3) The hot gas produced due to powder explosion is sprayed from the improved powder-actuated fastener-driving device onto the user in a rearward direction, thereby resulting in a discomfort feeling to the user.(4) Since the sound-absorbing sleeve moves synchronously with the inner tube, a larger force is required to move the sound-absorbing sleeve between two positions.